Head gasket, or ?????

[Hwyman]

I have a 66 coupe, 1968 302 block, fairly aggressive Crower roller cam, hyd. lifters, roller rockers, alum. heads. The motor has about 300 to 400 miles on it.
About two weeks ago I got on it a little (opened secondaries) and the heater hose came off the fitting on the intake manifold. Put it back together and checked all the other clamps. They were all just a little loose, so I figured the heater hose just wasn't tight enough.
Today I jumped on it pretty good up through 3rd gear. There is now water coming out between the intake and the head just above #4. I can see the gasket is blown out there and the water just flows out with the motor running.
I would think head gasket, but I checked compression and all cylinders had 130 to 140, with most at 135. If the head gasket was letting pressure in the the water jacket, wouldn't compression be down on that cylinder.
I know I have to take the intake off and replace the gaskets, but should I pull the heads at the same time, or put the intake back on and then use the tester to check for combustion gasses in the radiator. Any thoughts on what the problem may be are appreciated.

[GypsyR]

Sounds like you just have a leaking intake gasket. Some gaskets fit on aftermarket heads better than others. They might not have fit well enough to start with.

[Hwyman]

Thanks, hopefully that is it and I can fix it in a couple of hours. I was just worried that the two times I got on it, I seemed to have some sort of blow out in the cooling system, like a sudden over pressure. The attached picture is the latest problem.

[Maxum96]

I have split aftermarket intake gaskets in the past when I torqued the intake manifold down unevenly or too tight. I seriously doubt you have a blown head gasket. Your radiator cap would relieve the pressure once it got above 14-16psi or whatever it's rated at.

[Huskinhano]

Chinese intake manifold? Possibly the machining is off and may not have a good seal.

[GT289]

Doubtful on the head gasket.....
Milled heads & un-milled intake?
Or maybe just crappy intake gaskets.
Try using water only when you replace the intake gaskets-
saves on your coolant expenses. If you get no leaks, drain
and refill with antifreeze.

[LindenBruce]

I would use a Fel-Pro blue strip intake gasket along with a thin film of ultra blue silicon sealer around each port on both side of the gasket. They are reinforced to help prevent blowouts. If that was an un-reinforced gasket it could blow as you found out. In the pic the gasket looks like it's a plain Jane "racing" gasket. Those really are not made for long term endurance. I have a set of those that I used only for mock-up during my engine build. Bruce